Constant tension winding apparatus

ABSTRACT

A simple, inexpensive, all-mechanical apparatus which provides a varying force relationship on a roll means that automatically and exactly compensates for the depletion or increase of the material wound on a roll comprises a web roll means, a web tensioning means for applying tension to the web, and a sensing means coupled with the web tensioning means on a movable follower arm means. The web tensioning means includes a brake disc and a brake means contacting the disc and applying a braking force to the disc at a point generally along a radius thereof as determined by the movement of the sensing means in contact with the outer peripheral surface of the roll. The follower arm means is generally tangentially oriented with respect to the roll and is arranged so the brake friction moves the sensing means against the roll outer surface. In the embodiments shown the brake means and sensing means may be on the same or opposite ends of the follower arm means.

United States Patent n91 Staats 1March 13, 1973 1 CONSTANT TENSION WINDING APPARATUS [75] Inventor: Henry N. Staats, Deerfield, lll.

Primary Examiner-Leonard D. Christian AtmrneyHill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A simple, inexpensive, all-mechanical apparatus which provides a varying force relationship on a roll means that automatically and exactly compensates for the depletion or increase of the material wound on a roll comprises a web roll means, a web tensioning means for applying tension to the web, and a sensing means coupled with the web tensioning means on a movable follower arm means. The web tensioning means includes a brake disc and a brake means contacting the disc and applying a braking force to the disc at a point generally along a radius thereof as determined by the movement of the sensing means in contact with the outer peripheral surface of the roll. The follower arm means is generally tangentially oriented with respect to the roll and is arranged so the brake friction moves the sensing means against the roll outer surface. In the embodiments shown the brake means and sensing means may be on the same or opposite ends of the follower arm means.

3 Claims, 4 Drawing Figures CONSTANT TENSION WINDING APPARATUS BACKGROUND OF THE INVENTION This invention relates to a reeling and unreeling apparatus and more particularly concerns a device which maintains a constant tension in an elongated web of material as it is wound or unwound from a roll by automatically varying a braking force on a disc in direct relation to the varying size of the roll. As a result, the restraint or tension in the web is substantially the same for a full roll as it is for an empty roll condition and depends only upon the constant restraint provided at the actual brake location.

Many manufacturing processes utilize a web of material which is unwound from a roll. It is well known that some restraint or braking force must be applied to the roll, its shaft, or the web itself to keep the web taut and wrinkle-free. A taut web is essential in printing presses to prevent smearing of ink and to obtain good registration. In laminating machines where two or more task proportionally to keep tension approximately constant. In other words, an unwinding roll requires not only restraint, but, ideally, a restraint which provides constant web tension regardless of the web roll diameter.

Obtaining this ideal restraint is a difficult thing to do inexpensively and in a small physical space as required for example in commercial, business office laminators.

' Machines of this type rely mainly on braking the film roll shaft to provide sufficient web tautness to eliminate wrinkles in the web. However, in laminating machines, there are usually two film supply rolls whose webs come together to form the lamination. If the rolls are of a difi'erent size, the tautness of each of the webs will be different and this results in objectionable, curled laminates. Further, a fixed restraint at the shaft has the result that as a full roll unwinds, the restraint will increase as the roll moves toward the empty condition. It is not unusual then when an average braking adjustment is made to have too little restraint on a full roll and not enough of restraint with a more depleted roll. As diameters of film supply rolls increase, as they inevitably do because of commercial, long run require- I SUMMARY OF THE INVENTION Thedisadvantages of the priorart are overcome by the'simple, inexpensive, all-mechanical apparatus according to my invention which provides a varying force relationship on a roll means that automatically and exactly compensates for the depletion or increase of the material wound on the roll. As a result, the restraint or tension in the web is substantially the same for a full roll as it is for empty roll condition. My apparatus comprises a web roll means including a roll varying in size, a sensing means responsive to the variation in size of said roll, and a web-tensioning means coupled with the sensing means to maintain the tension applied to the web constant regardless of the size of the roll. The tensioning means and the sensing means are both mounted on the same movable follower arm means. The webtensioning means includes a brake disc rotating in direct relation to the rotation of the roll and a brake means contacting the disc and applying a braking force to the disc at a point generally along a radius thereof. The sensing means has a portion thereof contacting the outer peripheral surface of the roll and, being coupled with the tensioning means, moves the brake means along the radius of the disc in direct relation to the variation in diameter of the roll.

Both the sensing means and the brake means are attached to a follower arm means which is generally tangentially oriented with respect to the roll.'The point of contact of the brake means with the disc is spaced from a first pivot point of the follower arm means and is beyond, in the direction of rotation of the roll, the point of tangency between a circle having a diameter equal to the effective disc diameter and a' line tangent thereto passing through the first point. By means of this point of contact between the brake means and the disc a force component of the braking force will urge the sensing means into contact with the outer peripheral surface of the roll so that the assembly will work in an inverted position.

In a first embodiment of the invention the follower arm means includes first and second arms each pivoted about their respective first point. The arms extend about the disc and engage opposite sides incaliper-type relation. The first arm carries an element of the brake means and a sensing means that rests on the roll and follows its diameter exactly from a full to empty condition. The second arm carries another element of the brake means. A pressure adjustment means connected between the arms in caliper-type relation exerts an absolute restraint upon the disc which is dependent upon the tightness of the pinch, the area of the brake pad elements, and the coefficient of friction of the pads with respect to the disc. The restraint at the brake pads is arbitrarily set at a value and maintained at that value. As film is depleted from the roll and the restraining brake pads follow the changing roll diameter and move the brake means generally along a radius of the disc closer to the center of the disc, the mechanical advantage, or what may be referred to as their moment arm, is reduced. Thus, change in roll size during use provides a compensating change in brake pad location so that film tension will be constant from a full to an empty roll condition. Correspondingly, the actual tension in the film web is dependent "only upon the adjustable restraint at the-brake pads. v

In an embodiment of the invention applied to an unwind brake, the sensing means is located on one end of a follower arm means pivoted about its central region and the web tensioning means is located at the other end of the follower arm means. The sensing means contacts a driven roll on which the web is being wound and moves the brake means generally along the radius of a brake disc rotating about an axis parallel to and spaced from that of the roll means. The brake disc is connected to a co-axial disc roll against which the web is held by a biased idler roll. Again, as the follower arm means changes position as a result of the sensing means accommodating the roll size change, the brake means alters its position on the brake disc to maintain its fixed proximity to the web and thereby assure that constant tension is provided to the web regardless of the roll size.

From the above summary of the invention it may be seen that I have provided an apparatus in which web tension is independent of roll diameter being wound or unwound. Constant tension in webs being wound or unwound permits production of goods without fear of wrinkling, stretching or breaking due to a change in tension during production. In a situation where there are two or more rolls such as in laminating, the ability to obtain identical web tension permits production of laminated webs without curl and essentially independent of roll supply diameter. Moreover, the apparatus is simple and efficient in production, operation and maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

FIG. 1 is a schematic perspective of an embodiment of the invention;

FIG. 2 is an elevational view of a portion of the apparatus of FIG. 1 showing the caliper brake web tensioning means;

FIG. 3 is an elevational end view of the apparatus of FIG. 1 illustrating the angle off-set location of the follower arm means; and

FIG. 4 is a schematic elevational view of another embodiment of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A means for maintaining constant tension in moving webs generally indicated at in FIG. 1 comprises a roll means 12 and a web tension means 14 mounted together with a sensing means 16 on a follower arm means 18.

The follower arm means 18 includes a first follower arm 20 and a second follower arm 22 each connected at a first end or point thereof, 20a, 22a, by universal joints 24, 26, respectively, to a fixed shaft 28. The universal joints 24, 26 include a vertical pivot axis 240, 26a and a suitable bushing means 24b, 26b rotating about a horizontal axis to allow universal movement of the arms at the first point 20a, 22a. The arms 20, 22 may be generally parallel to each other, may be oriented generally tangentially with respect to the roll means 12, and of a length to engage the roll means 12 and the web tension means 14.

The roll means 12 includes a roll of an elongated web material 32 rolled on an elongated shaft 34 having suitable rotational bearing means 36 at opposite sides of the roll 30. A brake disc 40 having opposite first and second sides 40a, 40b, respectively, is also mounted on the shaft 34 adjacent the roll 30 to rotate in direct relation to the rotation of the roll.

A brake means generally indicated at 44 is attached to a second end area 20b, 22b, of each of the follower arms 20, 22 and engages the opposite sides 40a, 40b of the brake disc 40 in caliper-like relation. The brake means 44 includes brake pads 46, 48 attached to the first and second follower arms 20, 22 respectively. A pressure adjustment means 50 extending between the first and second follower arms 20, 22 in caliper-like relation allows mechanical variation of the contact pressure between the brake pads 46, 48 and the disc 40. The brake pads 46, 48 are adjustably engaged onto the brake disc 40 so that an absolute restraint is exerted upon the disc and depends upon the tightness of pinch, the area of the brake pads, and the coefficient of friction of the pad with respect to the disc. The restraint at the brake pads 46, 48 is arbitrarily set at a value and maintained at that value.

A sensing means 51 is attached to the first arm means 20 at the second end thereof 20b adjacent the brake pad 46 and rides upon the roll means 12 so that as the web material 32 is depleted from the roll 30, the restraining brake pads 46, 48 follow the changing roll diameter and move in exact fixed relationship to the outer diameter of the roll and the web closer to the center of the brake disc 40. Thus, a change in roll size during use provides a compensating change in brake pad locations on the disc so that film tension will be constant from a full to empty roll condition.

The brake means 44 and the follower arm means can be spring biased so as to always follow the web roll as it is depleted and so that the assembly will work in any position including an inverted position. This biasing means may be eliminated, l have discovered, if the point of contact of the brake pads 46, 48 with the disc 40 are located off center as shown in FIG. 3, because the rotation of the brake disc 40 will urge the brake pads 46, 48 towards the web roll so that spring biasing is not required. Further, the movement toward the web roll is of sufficient, force to overcome gravity and permit the mechanism to be operated in an inverted position. As shown in FIG. 3, this condition occurs where the point of contact of the brake means 46 with the disc 40 occurs beyond, in the direction of rotation of the disc 40, a point of tangency 62 between a circle 64, indicated in dotted lines, of a diameter equal to the effective disc diameter, and a tangential line 66 passing through the pivot point 28a, here the axis of the fixed shaft 28. With the pad 46 engaging the disc surface 40a, a force 68 at the point 60 directed along a tangent to the circle 64 will act upon the arm 20. The effective position of the arm 20 is indicated in dotted lines.

The force 68 may be factored into a force 70 acting through the pivot point 28a and a force 72 acting normal to the follower arm 20 urging the sensing means 50 into contact with the outer peripheral surface of the roll 30.

FIG. 4 schematically illustrates an adaptation of the invention to a winding apparatus wherein a web 132 is unwound from a supply roll 131 onto a roll 130. The roll 130 is driven by suitable means schematically illustrated at 133 and rotates about an axis 134. A web tensioning means 114 includes a brake disc 140 connected to a brake roll 141 and rotating coaxially therewith about an axis 142.

A follower arm means generally indicated at 118 has a generally central pivot point 119 fixed to a suitable support 128. A sensing means in the form of a follower wheel 150 is attached to a first end 1 18a of the follower arm means 118 and a brake means 144 is attached to the opposite end of the follower arm means 118. The brake means 144 may include a brake pad 146 biased into engagement with a surface 140a of the brake disc 140 to provide a restraining force to slow the rotation of the disc 140 and the brake roll 141. An idler roll 180 attached to a pivot arm 182 is biased against the brake roll 141 by suitable means 184 to allow tensioning of the web by the brake roll 141. It may be thus seen that the sensing means 150 follows the increasing size of the roll 130 and, being coupled to the brake means 144, changes the position of the brake pad 146 on the disc 140 so that it remains in fixed proximity to the winding web.

From the above description of the invention it may be seen that I have provided a simple, inexpensive allmechanical apparatus to vary the point of the application of a braking force to a roll means in exact compensation for the depletion or increase of the material wound on the roll. The relationship of the braking force to the web remains constant to produce constant web tension.

Although minor modifications might be suggested by those versed inthe art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonable and properly come within the scope of my contribution to the art.

I claim:

1. An apparatus for maintaining constant tension in a moving web comprising a web roll means having a roll varying in diameter, said roll having an outer peripheral surface, a web tensioning means for applying tension to said web, a sensing means contacting on said outer peripheral surface to move responsive to the variation in diameter of said roll, said sensing means being coupled with said web tensioning means to move said web tensioning means with said variation in size of said roll to thereby maintain the tension applied to said web constant despite the variation in the size of said roll, said tensioning means include a brake disc having a radius, said disc rotating in direct relation to the rotation of said roll, a brake means contacting said disc and applying a braking force to said disc at a point generally along a radius thereof, said sensing means contacting said outer peripheral surface of said roll and thereby moving said brake means along said radius of said disc in direct relation to the variation in diameter of said roll whereby a constant tension is imparted to said web, a follower arm means generally tangentially oriented with respect to said roll, said follower arm means being pivotally connected to a support at a first pivot point, said sensing means and said brake means being affixed to said follower arm and spaced from said first point,

and said point of contact of said brake means with said (llSC is beyond, in the direction of rotation of said dlSC,

the point of tangency between a circle of a diameter of the effective disc diameter and a tangential line passing through said follower arm pivot point.

2. An apparatus for maintaining constant tension in a moving web comprising a web roll means having a roll varying in diameter, said roll having an outer peripheral surface, a web tensioning means for applying tension to said web, a sensing means contacting on said outer peripheral surface to move responsive to the variation in diameter of said roll, said sensing means being coupled with said web tensioning means to move said web tensioning means with said variation in size of said roll to thereby maintain the tension applied to said web constant despite the variation in the size of said roll, said web tensioning means and said sensing means each including an arm, said arms each having a universal joint at a respective first point thereon, said universal joints mounting each of said respective arms at a fixed point, and a biasing means urging said arms to pivot about their respective first points towards each other.

3. An apparatus for maintaining constant tension in a moving web comprising a web roll means having a roll varying in diameter, small roll having an outer peripheral surface, a web tensioning means for applying tension to said web, a sensing means contacting on said outer peripheral surface to move responsive to the variation in diameter of said roll, said sensing means being coupled with said web tensioning means to move said web tensioning means with said variation in size of said roll to thereby maintain the tension applied to said web constant despite the variation in the size of said roll, said web tensioning means including a brake disc coaxial with said roll and having a radius, said disc rotating in direct rotation to the rotation of said roll, a brake means contacting said disc and applying a braking force to said disc at a point generally along a radius thereof, said sensing means contacting said outer peripheral surface of said roll and thereby moving said brake means along said radius of said disc in direct relation to the variation in diameter of said roll whereby a constant tension is imparted to said web, and including follower arm means generally tangentially oriented with respect to said roll, said follower arm means being pivotally connected to a support at a first pivot point, said sensing means and said brake means being affixed to said follower arm means including a first and second arm, said first point of connection of said first arm being spaced from said first point of connection of said second am, said first arm carrying said sensing means and a portion of said brake means, and said second arm carrying another portion of said brake means, said arm having a pressure adjustment means connected therebetween to mechanically vary the constant pressure of said brake means with said disc. 

1. An apparatus for maintaining constant tension in a moving web comprising a web roll means having a roll varying in diameter, said roll having an outer peripheral surface, a web tensioning means for applying tension to said web, a sensing means contacting on said outer peripheral surface to move responsive to the variation in diameter of said roll, said sensing means being coupled with said web tensioning means to move said web tensioning means with said variation in size of said roll to thereby maintain the tension applied to said web constant despite the variation in the size of said roll, said tensioning means include a brake disc having a radius, said disc rotating in direct relation to the rotation of said roll, a brake means contacting said disc and applying a braking force to said disc at a point generally along a radius thereof, said sensing means contacting said outer peripheral surface of said roll and thereby moving said brake means along said radius of said disc in direct relation to the variation in diameter of said roll whereby a constant tension is imparted to said web, a follower arm means generally tangentially oriented with respect to said roll, said follower arm means being pivotally connected to a support at a first pivot point, said sensing means and said brake means being affixed to said follower arm and spaced from said first point, and said point of contact of said brake means with said disc is beyond, in the direction of rotation of said disc, the point of tangency between a circle of a diameter of the effective disc diameter and a tangential line passing through said follower arm pivot point.
 1. An apparatus for maintaining constant tension in a moving web comprising a web roll means having a roll varying in diameter, said roll having an outer peripheral surface, a web tensioning means for applying tension to said web, a sensing means contacting on said outer peripheral surface to move responsive to the variation in diameter of said roll, said sensing means being coupled with said web tensioning means to move said web tensioning means with said variation in size of said roll to thereby maintain the tension applied to said web constant despite the variation in the size of said roll, said tensioning means include a brake disc having a radius, said disc rotating in direct relation to the rotation of said roll, a brake means contacting said disc and applying a braking force to said disc at a point generally along a radius thereof, said sensing means contacting said outer peripheral surface of said roll and thereby moving said brake means along said radius of said disc in direct relation to the variation in diameter of said roll whereby a constant tension is imparted to said web, a follower arm means generally tangentially oriented with respect to said roll, said follower arm means being pivotally connected to a support at a first pivot point, said sensing means and said brake means being affixed to said follower arm and spaced from said first point, and said point of contact of said brake means with said disc is beyond, in the direction of rotation of said disc, the point of tangency between a circle of a diameter of the effective disc diameter and a tangential line passing through said follower arm pivot point.
 2. An apparatus for maintaining constant tension in a moving web comprising a web roll means having a roll varying in diameter, said roll having an outer peripheral surface, a web tensioning means for applying tension to said web, a sensing means contacting on said outer peripheral surface to move responsive to the variation in diameter of said roll, said sensing means being coupled with said web tensioning means to move said web tensioning means with said variation in size of said roll to thereby maintain the tension applied to said web constant despite the variation in the size of said roll, said web tensioning means and said sensing means each including an arm, said arms each having a universal joint at a respective first point thereon, said universal joints mounting each of said respective arms at a fixed point, and a biasing means urging said arms to pivot about their respective first points towards each other. 